In 1962, scientists working on Cozumel Island, off the east coast of the Yucatan Peninsula, trapped 16 harvest mice and determined that they were a distinct species. None have been reported since, so they are classified as critically endangered. They were large for harvest mice, averaging about 20 g. in weight. To put this in perspective, a United States five-cent coin (a nickel) weighs about 5 g, so four nickels would balance one Cozumel Island Harvest Mouse on a scale. They had short, sparse fur and long tails. The 16 that were examined in 1962 were caught in tangled vines and in traps set at the base of trees and along stone walls in the forest. Nothing is known about this mouse's lifestyle or reproduction, but the 16 that were found, in August, included both adults and juveniles.